Salt has been used for many years to control the formation and accumulation of snow and ice on roads. Salts such as sodium chloride and magnesium chloride are spread onto roads either as solids (e.g., rock salt) or aqueous brine solutions, to lower the freezing point of the water on the roads. Sand, gravel and other abrasives are also placed on roads to increase the coefficient of friction between the road and the vehicles tires. Unfortunately, both salt and abrasives can cause signification damage to the environment and property.
The salt dumped on the roads can have an adverse impact on adjacent vegetation. In ecologically fragile areas, such as freshwater lakes and wetlands, salt migration from the roads can be particularly damaging to the surrounding flora and fauna. In addition, the salt can have corrosive effects on vehicles, causing rust and corrosion on vehicle paneling, chassis, exhaust systems, etc. The cumulative environmental and economic impact of these problems has caused many states to limit the use of salt on roads.
Similarly, sand and gravel can cause significant property damage when particulates kicked up by fast moving vehicles can dent vehicle paneling and crack vehicle windshields. In addition, loose particulates remaining on a road can reduce the coefficient of friction and create a vehicle slipping or skidding hazard. As a result, many states and regions restrict or prohibit the use of sand and gravel on roads, even when ice and snow are present.
More recently, mixtures of salt and carbohydrates have been introduced to control ice formation on roads. These mixtures significantly reduce the amount of salt needed for the mixture to provide useful lowering of melting points for road ice and snow. The reduced salt content lowers the environmental and economic damage caused by the mixtures.
The carbohydrates used have included sugars, such as monosaccharides like dextrose, maltose, malt-triose, as well as larger, more complex oligosaccharides and polysaccharides. Unfortunately, the large amounts of sugars used in these compositions (e.g., typically more than 5%, by weight, of the mixture) makes the mixtures expensive. In addition, may of the salt and sugar mixtures do not lower the freezing point to the desired temperature. The mixtures may also contain high levels of insoluble materials, making it more difficult to mix them into a liquid de-icing composition. Some of the materials used, such as phosphate modified carbohydrates, may also have an adverse environmental impact.
Still more recent de-icing compositions have included mixtures of salts and larger carbohydrates, such as starches. In these mixtures, the starch component is used to increase the viscosity of the solution to keep the salt component close to the surface of a road. Typically, these salt and starch mixtures typically contain more than 6%, by weight, of starch to ensure a high viscosity. Unfortunately, the large quantity of starch required makes these mixtures expensive to manufacture and use. In addition, the high viscosities of these mixtures can dramatically reduce the friction coefficient of the road, creating a dangerous slipping and skidding hazard for vehicles. Thus, there remains a need for non-hazardous, environmentally friendly, and economically viable compositions to prevent the formation and buildup of ice and snow on roadways.